Process analyzer

ABSTRACT

A process analyzer for detection of an analyte in a liquid under analysis includes a base module and an exchangeable cartridge module. The exchangeable cartridge module comprises a sample taking device comprising a membrane configured to obtain a sample from the liquid under analysis. A first pump mechanism is configured to pump the sample away from the sample taking device. A second pump mechanism is configured to introduce a reagent into the sample. A measuring section is configured to perform a quantitative detection of the analyte in the sample. A degassing device is arranged downstream of the first pump mechanism and the second pump mechanism. The degassing device is configured to degas the sample.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2010/054402, filed on Apr. 1, 2010 and which claims benefit to European Patent Application No. 09168536.2, filed on Aug. 25, 2009. The International Application was published in German on Mar. 3, 2011 as WO 2011/023421 A1 under PCT Article 21(2).

FIELD

The present invention provides a process analyzer for determining an analyte in a liquid under analysis, and can be used, for example, as an immersion probe, a swimming probe, a tube probe or as a laboratory analyzer.

BACKGROUND

Process analyzers quasi-continuously perform analyses for a quantitative determination of an analyte in a liquid under analysis, such as in water, and find application, for example, in waste water treatment or drinking water control.

Since a process analyzer is generally not used in laboratories, and maintenance, repair, and refilling carrier liquid and reagents entail considerable effort, modular process analyzers are now available wherein low-maintenance or maintenance-free components are arranged in a base module, and components that are delicate, exposed to wear, or which contain reagents, are arranged in an exchangeable cartridge module. It is also possible to provide a plurality of different exchangeable cartridge modules, for example, comprising reservoir tanks and fluidic systems.

A modular structure of a process analyzer is described, for example, in EP 0 706 659 B1. A part of the fluidic system and a dialysis membrane are therein arranged in a cartridge module, whereas the pumps and the reservoir tanks for the carrier liquid and the reagent are provided in the base module.

It is desirable in principle to also arrange the used material, i.e., the carrier liquid and the reagent, in the cartridge module. However, this requires that only rather small volumes of carrier liquid and reagent are used. This, in turn, can be achieved by designing the fluidic system as a so-called microfluidic system, i.e., by designing the liquid conduits with small sectional areas, for example, sectional areas of less than a few square millimeters. Microfluidic systems are, however, inherently more trouble-prone than fluidic systems with larger sections.

SUMMARY

An aspect of the present invention is to provide a process analyzer comprising a base module and an exchangeable cartridge module, which analyzer is reliable and in which the reagent is stored in the cartridge module.

In an embodiment, the present invention provides a process analyzer for detection of an analyte in a liquid under analysis which includes a base module and an exchangeable cartridge module. The exchangeable cartridge module comprises a sample taking device comprising a membrane configured to obtain a sample from the liquid under analysis. A first pump mechanism is configured to pump the sample away from the sample taking device. A second pump mechanism is configured to introduce a reagent into the sample. A measuring section is configured to perform a quantitative detection of the analyte in the sample. A degassing device is arranged downstream of the first pump mechanism and the second pump mechanism. The degassing device is configured to degas the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a schematic illustration of a process analyzer formed by a base module and an exchangeable cartridge module;

FIG. 2 shows a longitudinal section of an embodiment of an analyzer;

FIG. 3 shows a top plan view on the cartridge module of the analyzer in FIG. 2; and

FIG. 4 shows an embodiment of a degassing device of an analyzer cartridge module.

DETAILED DESCRIPTION

The process analyzer of the present invention is formed by a base module which is basically not exchangeable and an exchangeable cartridge module that can be exchanged with little effort at regular intervals, for example, when the carrier liquid supply or the reagent supply is depleted or a component is defective. The cartridge module includes the entire fluidic system which can, for example, be of a microfluidic design, i.e., all liquid carrying elements have very small volumes or very small sectional areas of a few square millimeters at most, for example, a maximum of 10 square millimeters, or, for example, of less than five square millimeters.

In an embodiment of the present invention, the cartridge module comprises a sample taking device, for example, a dialysis device, with a membrane, for example, a dialysis membrane, for obtaining a sample, for example, a dialysate, from the liquid under analysis. In case of a dialysis, the sample is a dialysate formed by a carrier liquid and the analyte from the liquid under analysis, with the analyte migrating through the membrane into the carrier liquid. A first pump mechanism is provided for the purpose of pumping the carrier liquid from a carrier liquid reservoir tank which can, for example, be arranged in the cartridge module, to the sample taking device. A pump mechanism is to be understood as a mechanical system that pumps a liquid. The pump mechanism can, for example, be designed as a displacement pump. The pump mechanism is driven by an actuator system that can, for example, be arranged in the base module separately from the pump mechanism. The cartridge module can thus, for example, not include an actuator system. No carrier liquid reservoir tank is provided if the sample taking device is a filter for filtering a sample.

In an embodiment of the present invention, the cartridge module comprises a second pump mechanism for introducing a reagent from a reagent reservoir tank into the sample. It also applies to the second pump mechanism that the associated actuator system can, for example, be arranged in the base module. The cartridge module further comprises a measuring section for the quantitative determination of the analyte in the sample or in the dialysate. The measuring section can, for example, be an optical measuring section for the photometric quantitative determination of an analyte.

The cartridge module further comprises a degassing device for degassing the sample or the dialysate in the course of the liquid conduit that leads from the sample taking device to beyond the measuring section, the degassing device being arranged behind the two pump mechanisms. Seen in the flow direction, the degassing device is thus arranged behind the sample taking device and behind the two pump mechanisms. By arranging the degassing device behind the pump mechanisms, it is provided that gas bubbles are removed from the sample before the same flows into the measuring section. This is important because gas bubbles can lead to substantial errors during measurement, for example, in an optical measuring section in which the analyte is quantitatively determined by photometry.

Gas bubbles may be formed in a sample when the sample in the cartridge module becomes warmer, for example, due to a warm liquid under analysis that is present at the dialysis membrane. An acid reagent in the sample can further expel carbon dioxide gas. By arranging the degassing device behind the point where the reagent is introduced into the sample, it is provided that the expelled carbon dioxide gas is also removed from the sample before the sample flows into the measuring section. Reliability, measuring certainty and measuring accuracy are thus improved.

In an embodiment of the present invention, both pump mechanisms can, for example, be driven pneumatically by a pneumatic pump on the base module side. The pressure side of the pneumatic pump may be connected to an overpressure accumulator, and the suction side may be connected to a vacuum accumulator. The overpressure accumulator and the vacuum accumulator are arranged in the base module.

In an embodiment of the present invention, the degassing device comprises a gas-permeable degassing membrane which is connected to the pneumatic pump of the base module to generate a vacuum on the gas side of the degassing membrane. The pump mechanisms may, for example, be designed as pneumatically driven peristaltic pumps, each having two or three pump chambers. A single pneumatic pump can thus form both the actuator system of the two pump mechanisms and generate the vacuum on the gas side of the degassing membrane. For this purpose, it is merely necessary to provide corresponding valves to control the pump mechanisms or the peristaltic pumps, respectively. The reduction to a single pneumatic pump for driving the pump mechanisms and for the degassing device results in a substantial reduction in design effort and manufacturing effort. Less energy is further required for the operation of the analyzer which is of great importance in particular with battery-powered analyzers.

In an embodiment of the present invention, the degassing device can, for example, be formed by a groove-shaped degassing channel covered by a gas-permeable degassing membrane. The degassing channel may, for example, be formed as a groove in an injection molded base plate on which the degassing membrane is fastened in the region of the degassing device, e.g., by gluing or welding. The degassing channel can, for example, extend in a meandering manner. This allows realizing the degassing device and the degassing membrane with rather small areas. The degassing membrane can, for example, be configured as a hydrophobic membrane, for example, a Teflon membrane.

The volume of the degassing channel can, for example, be at least as large as the volume of the measuring section. It is thereby provided that the entire measuring section can be filled with a degassed sample volume and that there is no part of the sample in the measuring section that is not degassed.

In an embodiment of the present invention, the volume of the degassing channel can, for example, be at least as large as the sum of the volumes of the space proximal of the membrane of the sample taking device and the reagent introduced. In this manner, all of the sample volume of a measuring cycle, mixed with the reagent, can be degassed in the degassing device. Irrespective of which part of this sample volume eventually fills the measuring section, it is thus provided that the sample volume that has reached the measuring section has been degassed.

In an embodiment of the present invention, the degassing channel can, for example, be a reaction space in which the mixture of sample and reagent dwells for at least 10 seconds before it is pumped to the measuring section. A separate reaction chamber, used to wait for the reaction of the reagent with the analyte in the sample, is not needed. If the reagent is acidic and expels carbon dioxide gas from the sample, it is thus provided that the carbon dioxide gas is withdrawn from the sample at the very site at which it is formed. A change in the volume of the sample during the reaction with the reagent is thus avoided. The sample/reagent mixture dwells in the reaction space until the reaction of the reagent and the analyte is substantially finished. It is thereby provided that no further carbon dioxide gas is expelled from the sample after it has left the degassing device, which gas could impair or corrupt the subsequent measurement in the measuring section.

In an embodiment of the present invention, the cartridge module can, for example, comprise a carrier liquid reservoir tank and a reagent reservoir tank. The entire fluidic system is thus arranged in the cartridge module. The volumes of the two reservoir tanks are designed such that the reservoir will last for the duration of the normal mechanical functionality of the cartridge module. In this respect, it is feasible to dimension the entire fluidic system as a microfluidic system. The reservoir tanks may be provided on the cartridge module such that they are exchangeable.

In an embodiment of the present invention, the base module can, for example, comprise a photometric analyte sensor that is functionally associated to the measuring section on the cartridge module side. The base module thus comprises a photometer, wherein the measuring section of the photometer is formed by the measuring section in the cartridge module when the cartridge module is placed in the base module.

In an embodiment of the present invention, the degassing device can, for example, be arranged between the two pump mechanisms on the one hand and the measuring section on the other hand. It is thereby provided that the dialysate is completely degassed before entering the measuring section. The degassing device or the degassing channel, respectively, can, for example, be arranged immediately upstream of the measuring section. As an alternative or in addition, the degassing device may also be arranged along the measuring section itself. In this manner, the dialysate can also be degassed during the measurement in the measuring section. This is feasible for a photometric measuring section since gas bubbles may corrupt photometric measurement results, especially if the measuring section is a microfluidic measuring section.

FIG. 1 is a schematic illustration of a process analyzer 10 for a continuous or quasi-continuous quantitative photometric determination of an analyte, for example, phosphate, ammonium or nitrate, in water. The analyzer 10 is a stationary analyzer 10 and is mounted immersed in an aqueous liquid 11 under analysis, i.e., it is designed as a so-called immersion probe. The analyzer 10 comprises a base module 12 rigidly suspended from a tubing 13 and hanging in or just above the liquid 11 under analysis, and an exchangeable cartridge module 14 removably fastened to the base module 12 and immersed into the liquid 11 under analysis.

The entire fluidic system of the analyzer 10 is provided in the cartridge module 14. The cartridge module 14 comprises a carrier liquid reservoir tank 26 with a carrier liquid 24 connected to a sample taking device 16 via a conduit, which device is a dialysis device 16 in the present case. As its membrane 18, the dialysis device 16 has a dialysis membrane 18 that separates the dialysis chamber 52, in which the carrier liquid dwells during the dialysis, from the liquid 11 under analysis. The dialysis chamber 52 may, for example, be formed by a meandering groove whose grove opening is closed by the dialysis membrane 18. A first pump mechanism 22 is provided behind the dialysis device 16, the pump mechanism pumping the sample 20 or the dialysate from the dialysis device 16 to a degassing device 40.

The cartridge module 14 comprises a reagent reservoir tank 34 containing a liquid reagent 30 pumped to the degassing device 40 by a second pump mechanism 28. A standard solution reservoir tank 56 containing a standard solution 58 is further provided in the cartridge module 14, wherein a third pump mechanism 54 is provided downstream of the standard solution reservoir tank 56, seen in the flow direction, which pump mechanism pumps the standard solution to the degassing device 40, if needed

The three pump mechanisms 22, 28, 54 converge in a star-shaped manner just before the degassing device 40, as is particularly well visible in FIG. 3. The degassing device 40 is formed by a groove-shaped degassing channel 48 covered by a gas-permeable and liquid-tight degassing membrane 44 which is a hydrophobic Teflon membrane. The degassing channel extends in a meandering manner so that a relatively long degassing channel 48 is realized in a small area. On the side of the degassing membrane 44 opposite the degassing channel 48, the gas side 46 of the degassing device is arranged whose evacuation is controlled through a degassing valve 70 on the base module side.

The sample flows from the degassing device 40 to a photometer measuring section 32 and from there into a waste liquid tank 60 in which the waste liquid 62 is collected. The photometer measuring section 32 is functionally associated to a photometer 50 on the base module side which has a light source 64 and a receiver 66 between which a section of the dialysate conduit is arranged in the longitudinal direction, which section forms the photometer measuring section. In the present case, the analyte sensor 50 is designed as a transmission photometer. Alternatively, the photometer may, however, also be designed as a reflection photometer 50′, as illustrated in the embodiment in FIG. 2.

The pressure sources for driving the three pump mechanisms 22, 54, 28 are an overpressure accumulator 72 and a vacuum accumulator 76 in the base module 12. The three pump mechanisms 22, 54, 28 are designed as pneumatic peristaltic pumps. A respective pump actuator system 78 is associated to each pump mechanism 22, 54, 28, each actuator system being formed by three change-over valves 86. Each pump mechanism 21, 54, 28 respectively comprises three pump chambers 80 with respective elastic pump membrane 82 made of rubber or an elastic plastic material.

The rear side of each pump membrane 82 is connected to a change-over valve 86 via a pneumatic control conduit 84 on the cartridge module side, a control conduit coupling 87 and a pneumatic control conduit 85 on the base module side, the change-over valve selectively connecting the pump membrane 82 with the overpressure accumulator 72 or the vacuum accumulator 76. In this manner, either an overpressure or a vacuum is applied to the rear side of the pump membrane 82 so that the pump chambers 80 are filled or emptied. By successively filling and emptying the three pump chambers 22, 54, 28, a peristaltic pumping movement is caused.

For the purpose of generating a vacuum in the vacuum accumulator 76 and an overpressure in the overpressure accumulator 72, a pneumatic pump 42 is provided in the base module 12, whose pump inlet is connected to the vacuum accumulator 76 and whose pump outlet is connected with the overpressure accumulator 72. The pneumatic pump 42 is driven continuously by an electric pneumatic pump motor 43. The vacuum in the vacuum accumulator 76 and the overpressure in the overpressure accumulator 72 are limited, respectively, by a corresponding vacuum valve 88 or an overpressure valve 74, each connected to atmospheric air pressure. As an alternative, the pressure sensors may be provided in the accumulators, by means of which the pneumatic pump is activated or deactivated when pressure falls below a limit pressure or exceeds the same.

The degassing valve 70 controlling the vacuum in the degassing device 40 is connected to the vacuum accumulator 76.

All valves 86, 70 and the photometer 50 are controlled by a central control 68. All electric components are arranged in the base module 12.

FIGS. 2 and 3 illustrate an embodiment of an analyzer or a cartridge module 14, respectively. A difference from the embodiment illustrated merely schematically in FIG. 1 is the concrete design of the three pump mechanisms 22′, whose respective last pump chamber 80′ is formed by a single common pump chamber 80′. Another difference in FIG. 2 is the design of the analyte sensor 50′ as a reflection photometer.

As is clearly visible in FIGS. 2 and 3, the cartridge module 14 is substantially formed by a plate-shaped plastic part comprising the fluidic system conduits, the pump chambers 80, 80′, the dialysis module 16, the degassing device 40 as well as the measuring section 32′, and by the tanks 26, 34, 56, 62 set on the plate-shaped plastic part.

FIG. 4 illustrates an embodiment of a degassing device 40′, wherein a part of the degassing channel 48 at the same time forms the photometer measuring section 32.

For all embodiments of the degassing device 40, 40′, the volume of the entire degassing channel 48 is at least as large as the sum of the volumes of the dialysis chamber 52 proximally of the dialysis membrane 18 and the introduced reagent 30.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 

1-12. (canceled) 13: A process analyzer for detection of an analyte in a liquid under analysis, the process analyzer consisting of: a base module; and an exchangeable cartridge module, the exchangeable cartridge module comprising: a sample taking device comprising a membrane configured to obtain a sample from the liquid under analysis, a first pump mechanism configured to pump the sample away from the sample taking device, a second pump mechanism configured to introduce a reagent into the sample, a measuring section configured to perform a quantitative detection of the analyte in the sample, and a degassing device arranged downstream of the first pump mechanism and the second pump mechanism, the degassing device being configured to degas the sample. 14: The process analyzer as recited in claim 13, further comprising a base-module-side pneumatic pump configured to pneumatically drive the first pump mechanism and the second pump mechanism, wherein the degassing device includes a gas-permeable degassing membrane which is connected to the base-module-side pneumatic pump so as to generate an underpressure on a gas side of the gas-permeable degassing membrane. 15: The process analyzer as recited in claim 14, wherein the degassing device is formed by a degassing channel having a groove shape, the degassing channel being covered by the gas-permeable degassing membrane. 16: The process analyzer as recited in claim 15, wherein the degassing channel has a meandering course. 17: The process analyzer as recited in claim 15, wherein a volume of the degassing channel is at least as large as a volume of the measuring section. 18: The process analyzer as recited in claim 15, further comprising a dialysis chamber disposed proximally to a dialysis membrane and an introduced reagent, wherein a volume of the degassing channel is at least as large as a sum of the volumes of the dialysis chamber and the introduced reagent. 19: The process analyzer as recited in claim 15, wherein the degassing channel is provided as a reaction chamber in which a mixture of the sample and the reagent dwells at least 10 seconds before being pumped to the measuring section. 20: The process analyzer as recited in claim 13, wherein the degassing device includes a degassing membrane. 21: The process analyzer as recited in claim 20, wherein the degassing membrane is a hydrophobic membrane. 22: The process analyzer as recited in claim 13, wherein the exchangeable cartridge module further comprises a carrier liquid supply tank and a reagent supply tank. 23: The process analyzer as recited in claim 13, wherein the base module comprises a photometric analyte sensor which is functionally associated with the measuring section. 24: The process analyzer as recited in claim 13, wherein the degassing device is arranged between the first pump mechanism and the second pump mechanism, and the measuring section. 25: The process analyzer as recited in claim 13, wherein the degassing device is configured to degas the measuring section. 26: A cartridge module for a base module, wherein the cartridge module comprises: a sample taking device comprising a membrane configured to obtain a sample from a liquid under analysis, a first pump mechanism configured to pump the sample away from the sample taking device, a second pump mechanism configured to introduce a reagent into the sample, a measuring section configured to perform a quantitative detection of an analyte in the sample, and a degassing device arranged downstream of the first pump mechanism and the second pump mechanism, the degassing device being configured to degas at least one of the sample and the measuring section. 27: The cartridge module as recited in claim 26, wherein the cartridge module further comprises a carrier liquid supply tank and a reagent supply tank. 28: The cartridge module as recited in claim 26, wherein the degassing device is arranged between the first pump mechanism and the second pump mechanism, and the measuring section. 29: A cartridge module for a base module, wherein the cartridge module comprises: a sample taking device comprising a membrane configured to obtain a sample from a liquid under analysis, a first pump mechanism configured to pump the sample away from the sample taking device, a second pump mechanism configured to introduce a reagent into the sample, a measuring section configured to perform a quantitative detection of an analyte in the sample, a degassing device comprising a gas-permeable degassing membrane, the degassing device being arranged downstream of the first pump mechanism and the second pump mechanism, and being configured to degas at least one of the sample and the measuring section, and a base-module-side pneumatic pump configured to pneumatically drive the first pump mechanism and the second pump mechanism, wherein, the gas-permeable degassing membrane is connected to the base-module-side pneumatic pump so as to generate an underpressure on a gas side of the gas-permeable degassing membrane; and the base module comprises: a photometric analyte sensor which is functionally associated with the measuring section. 30: The cartridge module as recited in claim 29, wherein the cartridge module further comprises a carrier liquid supply tank and a reagent supply tank. 31: The cartridge module as recited in claim 29, wherein the degassing device is arranged between the first pump mechanism and the second pump mechanism, and the measuring section. 